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SAN FRANCISCO (KCBS) — The discovery of a suspicious package shut down a San Francisco Public Health Department building in the city’s South of Market neighborhood Monday morning.

The package was reported about 8:20 a.m. at 1380 Howard St.

Department of Public Health operations manager Charles Maranon described it as a black plastic box that was found chained to the building’s front gate.

He estimated that the box was about 3 feet long, 2 feet wide and 2 feet tall. There was no note or any explanation of why it was there, he said.

The box was discovered before the offices opened for the day, and employees arriving for work were told to wait outside. Deputy Director of Health Marcellina Ogbu said about 300 employees work at the building.

Maranon said the employees waited on the sidewalk on Ninth Street as a San Francisco Police Department bomb squad responded.

Howard Street was shut down between Ninth and 10th streets, and southbound traffic was gummed up on 10th Street as motorists were rerouted.

At about 10:40 a.m. a loud blast shook the neighborhood, setting off car alarms. Police Capt. Michael Redmond explained that the blast was from the bomb squad using a “water disruption tool” to break apart the box. He said police are still investigating what was inside the package.

Shortly after the blast was heard, a bomb squad member could be seen changing out of a heavy-duty protective suit on Washburn Street, an alley between Ninth and 10th streets. Meanwhile a homeless man slept nearby, apparently undisturbed by all the activity.

The Department of Public Health was the only building evacuated, but employees and residents in nearby buildings were advised to shelter in place, Redmond said.

Maranon said at about 11:20 a.m. that public health department employees were being let back into the building.

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